Multiple unit steerable antenna system



Dec. 24, 1940. D, H, RING MULTIPLE UNIT STEERABLE ANTENNA SYSTEM FiledJuly 14, 19:59

22 Sheets-Sheet l 3$ mm H UQMJ QQ H .N

uvva/vrop D. H. RING 5y i V q Dec. 24, 1940. D. H. RING MULTIPLE UNITSTEERABLE ANTENNA SYSTEM Filed July 14, 1939 2 Sheets-Sheet 2 INVENTORBy a/z /Nc 4 A T TORNE'V of either reception or transmission or both in.a multiple unit steerable antenna system.

UNITED STATES Patented Dee. 24, 1940 3 MULTIPLE. UNIT s EERgBnE SYSTEDouglas H. Ring, Red BankjN assi n ri Bell TelephoneLaboratories,Incorporated, New

.York, N.VY., a corporation of New Application July 14, 1930,-Se

11 Claims. (oi.,25 .,-1-1-) I invention" relates to radio communicationsystems, and more particularly to methods and means forcontrolling andimproving the quality "The invention is particularly concerned withmultiple unit antenna systems generally'of the 'typeclisclosed in Patent2,041,600 of H. T. Friis,

issued May 19, 1936.

-' -Qne'of theobjects of the invention is to effect bandwidthcompensation in order tofsecure a maximum output over a theoreticallyinfinite band of frequencies when the maximum lobe'of I 'amultiple unitantenna array issteered to coincide with the average incoming wave pathor angle of the incoming carrier wave. I

Another-object of the invention is to provide a method and means forpermitting the steering ofthe maximum lobe of the multiple unit arrayatdifierent operating frequencies without alterin'g the relativepositions of the phase changers foreach'operating frequency when thelengths of 'thehigh'fr'equency lines to the antennas are unequal,-- asin the-'case of a "system where the receiver is located at a pointintermediate the array, an ddo not vary progressively in a simple ratio;

Another object'of the inventionis to effect a saving in the amount ofhigh frequency transmission line required between-the antenna units andthe receiving station by locating the station at th middle, orat anyother convenient interinediatepointbetweenthe ends, of a long antennaarray. 1 l v v Otherobjects and features will appear hereinafter inconnection with the description of the preferred embodiments of theinvention.

' A multiple unit steerable antenna array, such 'as that disclosed inthe above-mentioned Friis patent, is an end=on system and is designed toreceive'waveszha'ving' a direction of arrival ,included "in the.vertical plane of the array, and ordinarily making an angle less thanforty degrees with the-horizontal. -In order to secure a maximum effectat the receiver for a given incoming direction, as, for example, ahorizontal direction, the out-of-phase wave components absorbed by thevarious antenna units must be rendered in phase, at the receiver bymeans of phase shifters included between the antennas andireceive'r. Tosecure the maximum output at the receiver, the arrangement should besuch that the various antenna units deliver to the receiver an in-phaseresultant for each of the simultaneously received frequencies includedin a side-band of the incoming signal at which the maximum" lobe of thearray is steered. If the unitfantennas of the "array are connected tothe receiver" or phase changers by lines of equal length the variouswave components will trav- 5 erse -plaths', of different lengths, forthereason that the; paths in "space from -a given wave front correspondingto a given incoming wavefdir'ecen rnq e i li I a 'llre delayor timeconsumed byafwave com- 10 ponentat'a giyen frequency in'travelingthrough the space' path and thence through the'line'path tothereceiver'is; directly proportional to the of *"thelparticularlpathtraversed; and for thepathso'f different lengths, the delays sui-"-fere'cl'tra'r'isrn i sls ion over the different length paths will-"be,imequal; For i a given single frequency correction or compensation forthe dif-" man e-1n pathlengths can be made by means of phaseshifter'S'f-One of the problemstoward the solution ofwhich the presentinvention is directed is that'of compensating; for all ofthe severalfrequencies that" constitute 'the carrier and its side-bands, and thussecuring maximum output over a very wide and theoretically infinite 5band of frequencies. f

Assuming ;a path of given length and several frequencies appliedthereto, the phase at the output end of the line for each frequency willdepend on thelength-of the line. If at a par-, ticular frequency thephase at the output end agrees with that at the input end, at anotherdifferent frequency simultaneously transmitted 'over' the path, thecorresponding phases at the ends of the path will be different, and therate ofv change. in the phase shift will increase with .frequency; Thatis, the delay or phase char- In order to secure a maximum combinedoutput at all frequencies, the delay, here defined as the rate ofphasechange with frequency, must be equal in the two paths. Since space andline paths have linear delay or phase-frequency char-- acteristics,it'is only necessary to make the over- 5 all characteristics the samefor all paths. In accordance with the present invention, the totalelectrical lengths of the several paths to the receiver, each of whichpaths comprises a space portion and line portions, are made equal. Thusthe delays in all paths are the same, and. at all frequencies in-phaseaddition occurs at the receiver.

Specifically, in the preferred embodiment of the invention hereindisclosed this result is accomplished by the inclusion in each path ofcompensating intermediate frequency lines of such length or delaycharacteristics as to make all of the paths equal in effective length tothe longest path for an assumed average incoming wave path or angle.This insures that the relative phase relations of the waves on all pathsto the receiver shall be the same, and. therefore that in-phasecombination shall occur at the receiver.

The steering or directing of the maximum lobe of a multiple unit antennaarray is a matter which involves the changing of the absolute phase ofthe signals received. For a given desired direction of reception theadjustment of the phase shifters differs with frequency; that is, if thereception of a wave of one frequency at a given steering angle isaccomplished by a progressive adjustment of phase shifters by a certainnumber of degrees differential between them, the reception of adifferent frequency at the same steering angle will require theadjustment of the phase shifters at a different number of degreesdifferential between them. If the lines from the antennas to thereceiver are of equal length or differ in length in accordance with asimple ratio, the phase changers may be driven through gears having theratio 1, 2, 3, etc. for steering purposes. But if the lines are unequaland do not vary in such simple ratio, the phases of the wave componentsefiective at the phase changers do not correspond with the phases at theantennas, and the steering control of the array is impaired.

In accordance with another feature of the present invention, whateverphase changes are introduced by dissimilar antenna spacing andcorresponding differences in the lengths of the high'frequency linesconnecting each antenna to the associated first detector arebalanced oreliminated by establishing a certain relationship between the lengths ofthe beat oscillator lines and the corresponding antenna high frequencylines extending to the first detectors of the various antenna units; asby making each beat oscillator line that extends to a certain detectorequal in length to the high frequency line that extends from the antennato that same detector. With this relationship established, upon a changein beat oscillator frequency, in the process of tuning to a differentincoming frequency and at the same time maintaining the intermediatefrequency constant, the same absolute frequency change occurs in thebeat oscillator line frequency as occurs in the frequency that is cominginover the high frequency line. This has the effect of changing thephases equally. Since the beat oscillator is common to all detectors,the intermediate frequency currents have the same relative phases at thenew frequency as they had at the original frequency. Signal wave delayis not affected since the line from the beat oscillator does not conveythe signal currents.

The invention will be more readily understood from the followingdetailed description, when taken in connection with the accompanyingdrawings in which:

Fig. 1 illustrates one embodiment of the invention, in which thereceiving station is located intermediate the ends of the antenna array,in which the irregularities in the lengths of the paths are equalized bythe introduction of compensating delay means in the intermediatefrequency portions of the paths, and in which steering compensation fortuning changes is effected by proportioning the lengths of the beatoscillator paths to the lengths of the corresponding high frequencyantenna lines; and

Fig. 2 illustrates a modification in which the compensating delay meansare introduced in a common portion, instead of in individual portions,of the intermediate frequency lines, and the steering is lined up on anintermediate instead of the rear antenna unit.

Referring to Fig. 1, reference characters A1 to Av'des ignate an arrayof horizontal rhombic receiving antennas assumed to extend in the planeof the. great circle including the distant cooperating station withwhich communication is desired. The antenna units are not'necessarily ofthe rhombic type, but may be any type of directive unit. The assumeddirection of. the incoming wave is indicated by any of the arrows S1 toS7. The wave direction may be included in the vertical plane containingthe longitudinal array axis, or in a. vertical plane angularly relatedto the axis, that is, the angle between the wave front and the arrayaxis may bein any vertical plane or in a horizontal plane.

Each of the antenna units excepting A4, which is at the receivinstation, is connected along the array by a corresponding high frequencyline HE'i to HFq, usually a coaxial, line, with its correspondingmodulator or first detector D1 to D1. Each of the first detectors isconnected with a corresponding phase changer P01 to PCq by way of thecorresponding intermediate frequency lines IF]. to IE7. The combined.outputs of the branches controlled. by the phase changers pass by way ofintermediate frequency amplifier IFA, low frequency detector LFD and lowfrequency amplifier LFA to the translation device T, which, in thepresent intance, is assumed to be a radio signal receiver.

'At each of the first detectors D1 to D7 the incoming energy from the.corresponding antenna units is intermod-ulated with the energy of a highfrequency wave supplied by the beat oscillator BO over the beatoscillator line BOL and its various branches. The beat oscillator andits line, as shown, are assumed. to be located at the receiving station.

The circuit interconnections between the various elements arerepresented in part by light lines and in part by heavy lines. The lightlines represent portions of the interconnections in which thetransmission delay over the. circuit is either inconsequential or is thesame for all paths. The heavy lines represent portions of theinterconnections having transmission delays which constitute factors inthe equalization toward which the present invention is particularlydirected.

Assuming first that the direction of reception is at zero angle, thatis, a wave arriving in the horizontal plane of the antenna array and ina direction coinciding with the array axis, it is evident that the wavefront, which in the assumed case is vertical, reaches the antenna A7first and passes thes'uccessiveantennas of the "array; finally passingantenna A1. 1

- "With the antennas spaced apart by intervals D, whichlmay be assumedto be equal, the length traversed by the wave in its passage fromantenna Avto' antenna A -is equal to 6D. Considering antenna- -A7', -'asthe reference point, the length of the space path to'antenna A6 is D, toA5 is2D, t'-}A4- 'is= 3D, to A3 is 4D, to A2 is 5D and to antenna: A1fis 6D. If the angular direction of approach of the waveis greater thanthe zero an'gle, the-lengths of the'various space paths to thesu'cc'essive antennas of the array, represented by S1 to S7 for thevarious units, are diminished over the horizontal spacing intervals Daccording to' the'co'sine 'of the angle between the wave di- 1 wavefront through each antenna to the cormotion and; the array axis.Multiple unit-steerable antenna arrays of this characterareordinarily'designed to be steered at any angle be- 205.

tween; zero and approximately forty degrees. The transmission path fromthe advancing responding-phase changer is made up of a space portion, ahigh frequency transmission line por-,

tion, and an intermediate frequency transmission line portion. -Thecondition that mustbe satisfi'edin order that the relative phases at'theoutputsfofall of the paths shall remain fixed'for all frequencies andshall therefore add properly at the receiver, is that the effective or.electrical lengths of all of the'paths from the advancing wave front byway-ofthe antenna units to the receiver shall be equal. In thearrangement shown in Fig. 1, there is a wide diversity in the respondingfirst detectors.

lengths ofthe respective paths from the advancing wave front, shown asthe broken line WF intersecting the antenna A7, to the cors pace portionof the path from the advancing wave front to antenna A1 is 6D cosine 6and the I high frequency line portion of the path by way of I-IE1 has alength of 3D. Proceeding alongthe resented as follows:

line of the array each succeeding space path is 'diminishedby D cosine 6until at antenna Aqthe length of the space path is zero. On

account of the central disposition of the receiving station with respectto the antenna array, in 'theembodiment of the invention shown, thelength of the highfrequency line becomes 2D for antenna A2, D forantenna A3, zero for antenna A4, D for antenna A5,,2D for. antenna A6and 3D forf antenna A7. Therefore, the. length. of the paths as far asthe first detectors may be rep- Antenna Space 6D cos. 5.." 5D cos. 5..-.

" Space paths and transmission lines have linear delay orphase-frequency characteristics; that is,.the phase shift is a linearfunction of frequency, and the delay or rate .of change of phase Y shiftwith frequency is proportional to the length of the path or line, which,in the system under consideration, includes both space portions-andtransmission line portions. With paths of diverse lengths as indicatedabove, it is obvious that it several frequencies are being transmittedover the paths the phase shifts on the two paths will I differ at all,except possibly one, of the trans- The length of the I High frequencymitted frequencies whereby while complete phase agreement may result atthe-above-mentioned frequency when the line outputs are combined,"

phase disagreement of varying degree obtains at the remainingfrequencies and at some particular frequency the outputs are 180 degreesout of phase. Consequently, the outputs from the various lines cannot becombined in phase for all frequencies unless the lengths of the path aremade effectively equal.

As shown in the system of Fig. 1, this is accomplished by the inclusionin eachpath of compensating intermediate frequency lines of such lengththat-all the paths'from the various antennas of the array are made equalin length or delay to the longest path for the average assumed incomingwave direction or angle. In other words, the over-all delays in all ofthe paths are made equals By reference to the precedin'gtabulatiomitwill be seen that the longest path is that by way of antenna A1, thespace portion having a length of 6D cosine 6 and the high frequencytransmis- 'sion line portion having a length of 3D. Therefore, to makethe effective lengths of all the paths thesame, there is added'to thepath in each of the intermediate frequency lines IF1 to IFv, sufgficient length of line or its delay equivalent to bring the totalv foreach path up to 3D+6D cosine 6. The path lengths thus added in thevarious intermediate frequency lines are indicated on Fig. Land are asfollows:

' ponent frequencies are the same at the output terminals of thevarious. paths .and at each frequency the combined output energiesproduce a maximum -resultant,;and the .width of the frequency. band istheoretically infinite.

This is the relation which holds with respect to the particularangle ofincidence 6 that is chosen .When the maximum lobe of the array is.steeredfat a different angle of incidence, the

lengths of the space paths fromgthe'wave front' to the various units ofthe array are altered proportionatelyto the cosine of the new angle; and

slight alterations of the D cosine 6 additions to the variousintermediate frequency lines become necessary in order to maintain an.exact in-phase relationship between the output energies of the variouspaths. But in practice 'it is sufficient to proportion-theintermediatefrequency line additions to the mean or weighted average angle ofreception. When this is done the effect of variations in the steeringangle upon the proper phase relations at the output terminals of thepaths is minimized, and substantially in-phase combinations over-a broadband of frequencies are maintained.

' The ratio of the velocity of transmission through space to thetransmission velocity over the high frequency lines and the ratio of thevelocity in space to the transmission velocity over the intermediatefrequency lines are factors enteri'ng into the determination-of theexact values solute phases of: the various paths at the point where theoutputs are combined. For'the re-' of the additions in the intermediatefrequency lines to equalize the delays in all of the paths. For highfrequency and intermediate frequency lines ordinarily employed inreceiving systems these ratios are each equal to 0.933.

The conditions for infinite band width at any angle of incidence in thegeneral case have been derived and are expressed in the followingequation:

D cos. VS(LS2 LS1) +Vi(Li2-Li1) where 'D=a'ntenna spacing in meters5=between the array axis and the wave di-' rection for which efficientoperation over an infinite band width is desired vs ratio of spacevelocity to high frequency line velocity V1=ratio of space: velocity tointermediate frequency line velocity L51==length of high frequencysignal antenna I in meters Lsz length of high frequency line to'antenna2 in meters Ln 'length of intermediate frequency line in antenna I pathin meters Lizzlength of intermediate frequency line in antenna 2 pathin'meters The above equation shows that for any arbitrary lengths of L51and LS2 the conditions for th'eoreticallyinfinite bandwidths for anyangle of incidence may be fulfilled by correctly adjusting thedifference (Lz'2-Lil).

The steering of the maximumlobe or lobes of line to a multiple unitsteerable antenna system is a matter which involves the changing of theabception of any given frequency the steering of the maximum loberequires only the relative setting of all phases correctly, regardlessof the path delays. When the relative phases of the outputs of all thepaths are correctly set for the proper steering angle at a particularfrequency, the delays in the system determine the breadth of the band offrequencies that can be received without altering the relative positionsof the phase changing units.

In a system in which the high frequency lines from the antennas to thefirst detectors are equal, steering may be accomplished by gearing thephase shifters together in a 1, 2, 3, etc. ratio, and it will not benecessary to alter the relative phase changer settings when the systemis tuned to a new frequency. Also, if the high frequency lines from theantennas to the first detectors vary in any multiple of the gear ratios,compensation may be effected by turning the master control, and therelative phase changer settings will not need to be altered for changesin the frequency of the incoming carrier. An example of such a multipleunit array with uniformly spaced units and uniformly graded gear controlof the phase changers is presented in the previously mentioned patent toFriis.

Where, as in the present case, this simple relationship of antenna unitspacing and high frequency line ratios does not exist, means must beprovided for compensating for the departure from uniformly progressivephase differentials at the phase changers that is consequent upondissimilar antenna spacing and dissimilar variation in the relativelengths of the high frequency lines.

Assuming that the frequency in the intermediate frequency lines is to bemaintained constant, the frequency of the beat oscillator BO must bechanged for each. different high frequency carrier for which the systemis tuned. The'change in the frequency supplied by the beat oscillatormust correspond to and be the same as the frequency difference betweenthe carriers in tuning from one to another. Thus, if we assume a fixed 1frequency of one megacycle for the intermediate other, the absolutechange in frequency over the high frequency line is the same as theabsolute change in frequency over the line that extends to the firstdetectors from the beat oscillator. The change in phase shift on anyline of given length, however, is proportional to the absolute change infrequency and to the length of the line. Hence it is possible to addlengths of line to the beat oscillator paths to compensate for thechanges that take place in the signal carrier phases over theirregularly related lengths of :high frequency.

line when the tuning of the system is altered from one signal carrierfrequency to another. More specifically by making the two lines fromeach detector, one to the antenna and the other to thebeat oscillator,equal in length the phases of the beat oscillator waves supplied to thedetectors have the same relation, at any tuning frequency, as the phaseshifts introduced by the high frequency lines in the currents suppliedtothe detectors; and the output currents of the detectors have the samephase relation as the components' absorbed by the antenna units. Stateddifferently, the phase shift in each beat oscillatordetector linenullifies the phase shift introduced by the associated antenna-detectorline whereby the first detectors are in effect positioned at theterminals of the antenna units and directly connected thereto, and upona change in tuning frequency steering may be accomplished withoutcalibrating the phase shifters.

Such an arrangement is illustrated in Fig. 1 in which the effectivelengths of the paths from the beat oscillator B0 to the various firstdetectors D1 to D7 are made equal in each case to the length of highfrequency line that extends from each particular first detector to thecorresponding antenna of the array. In Fig. 1 it may be assumed that thelength of beat oscillator line from the oscillator to the point 01 is alength D, that the length of line from the beat oscillator to the point02 is 2D, and that the length from the oscillator to point 03 is 3D. Theconnections from point 01 are made to the two detectors D3 and D5, eachone of which is connected with its corresponding antenna by a length Dof high. frequency line; from the point 02 of the oscillator line BOLconnection is made with the two detectors D2 and De, each of which isconnected with its corresponding antenna by a length 2D of highfrequency line; and from the point 03 of beat oscillator line connectionis made with the two detectors D1 and D1, each of which is connectedwith its corresponding antenna over a length 3D of high frequency line.The connection of the {beat oscillator with the detector D4 is by meansof a connection which is directly from the oscillator and is assumed tobe of zero length to match the zero length of high frequency line whichis assumed to connect detector D4 with its correeach and spondingantenna. Thus, the beat oscillator is connected with the ,detectorsvoverbeat oscillator lines the lengths of which in each case are equal .tothe lengths of the corresponding lines from the detectors to theantennaunits of the array. I

When compensation for irregular phase change with tuning change has beeneffected as described above, the phase changers :may be geared to-;gether in a 1,2, 3, etc. ratio and all operated from a single driveshaft without adjustment upon a change in tuning frequency.

The relationships that must be established in order to satisfy thiscondition have been derived and are expressed in the following equation:

7 Vs (Ls1Ls2) +Vo (Lo2'-L01=AD where p I Ls1=length of high frequencyline to antenna linmeters Lsz=length of high frequency line to antenna 2in meters Lo1=length ofbeat oscillator line to detector l in meters ILoz=length of beat'oscillator line to detector 2 in meters r Vs=ratio ofspace velocity to high frequency line velocity 1 Vo=ratio of spacevelocity to beat oscillator I line velocity A=any constant, including 0D=antenna spacing in meters When the values of the different'factors areso chosen that the constants A have the same value for each and everypair of units inthe array, it is not necessary to alter the positions ofthe various I phase shifters when the system is tuned to a newfrequency. With beat oscillator lines'to the detectors having thelengths shown and described illustrated in Fig. 1. Thesystem of Fig.2 isgenerally the same as that of Fig. 1, withthe exception of the featuresthat will be described, and

1 reference characters the same as those of-Fig. 1,

are used for all elements illustrated excepting those which differ fromthe elements of Fig. 1.

In the system of Fig. 2 each of the first detectors or modulators D1 toD7 is directly connected with its associated phase changer P011 to PCrz.The outputs of all but PC11 of the phase changers are connected with thecommon'intermediate frequencyamplifier D 'A through part or all of thecompensating intermediate frequency line Each of the three sections ofthe line IF has a delay equal to 2D. The longest path, that by way ofantenna A4,

detector D1 and phase changer P011 is connected directly with theintermediate frequency amplifier IFA, and has no delay in this portionof the intermediate frequency circuit. The path from antenna A2 throughdetector D2 and phase changer P012 is so connected with the intermediatefrequency delay path that it suffersa compensating delay of 2D. Asshown, the path from x antenna A3 is delayed 4D in the intermediatefrequency path, and the branches from antennas A4 to A1 each include theentire length of the intermediate frequency; path IF and are eachdelayed 6D. For zero angle, of arrival of the signal wave .theover-alllengths ofall -of the paths are thus equalized, and thecondition for in-phasecombination for .maximum output over atheoretically infinite band of frequencies is established. r

7 Where the angle of arrival of the signal wave is greater than zero,--exact compensation may be effected by introducing additional smalldelays,

as by short pieces if-intermediate frequency line,

in the conductors connecting each of the first detectors D1 to Dr withits, corresponding phase changer. The proper'valuesfor such additionaldelays may, for instance, be secured by zero addition in the connectionfrom detector D1 to phase changer PO D(l.-;ccs.6) in theconnection fromdetector D6 to phase changer PC"1 and progres sively graded incrementsof 2, 3, 4, 5 and 6 times this value for the connections associatedwithdetectors D5, D4, D3, Dz-and D1,. respectively, as indicated in Fig. 2.These values may receive such slight modification as may be necessaryalso to compensate for the ratio of space velocity to line velocity. 4,v j a Another respect in which thesystem of Fig. 2

differs from'that' of Fig. 1 is' that in the Fig. 2'

system thesteering is lined upon themiddle antenna unit A4 instead ofthe rear antenna'unit ,A1, and the phase. changers are arranged in twoseparate groups. One group includes phase changers P011, P0 2- and P013and the other group includes phase changers P015, P016. and P017.

The phase changer PC 14 associated with the first detector of themiddle-antenna A lof the array is in a sense adummy, as thisantenna,.being.the referencewith respect to which the phases of theother two groups of antenna paths are shifted, requires no shifting ofphase in the steering oper ation. Each of the groups of phase changersis driven by a separatev shaft having uniformly graded gear connectionswith a 1, 2, 3. ratio, as

indicated in the drawing. The common driving mechanism is arranged todrive the two groups of phase changers in opposite directio v,

If it were assumed that the-beat oscillator BO were connected withthe'series of firstdetectors by measn of paths of'equal length, it wouldbe necessary in changingthe tuning of the system from one signal carrierfrequency to another to mechanically disconnect the shafts of" the twoone or the other of theshafts until the energy contributions of thetwogroups were in phase with each other, and thenagain recouple ,the'

shafts in the readjusted position But by virtue of the beat oscillatortuning compensation for diversity in length of the high frequencytransmission lines between each antenna and itsassocie ated firstdetector, as described inconnection with the system of Fig. 1, norelativeadjustment of thetwo groups of phase changersiis required whenthe tunin is changed from one signal car rier frequency to another. Thisis true as long as the beat oscillator frequency remains either above 1or below the carrier frequencyfor all tuning adjustments. If for anyreason it should become desirable to changethe beat oscillator frequencyother, then the provision of a clutch. between the groups of phasechangers would permit a relative readjustment of the two-groups toestablish the new relationship required by the change in the side of thebeat oscillator frequency with reference to the carrier. r 1

It will be understood that delay networks or from one side of thecarrier frequencies tothe o groups of phase changers from each other,rotate artificial lines constructed to have delay characteristicsequivalent to those of the compensating intermediate frequency lines orto the compensating oscillator lines may be substituted for such linesif desired. It will also be understood that the principles of theinvention may be utilized in an array designed for horizontal and/orvertical steering of the directional characteristic and that antennasdesigned for utilization of vertically polarized components instead ofantennas designed to employ horizontally polarized components may beused.

What is claimed is:

1. In a radio system, an antenna array com.- prising a plurality ofantenna units, a translation device, separate lines connecting saidtranslation device to each antenna unit and each having a Wave velocitydiffering from the wave velocity in space, and means included in certainof said lines for compensating for the difference in said line and spacevelocities, whereby the paths traversed by the wave componentsintercepting said units and extending from a desired wave front to thetranslation device are substantially equal in electrical length and havethe same delay or phase-frequency characteristic.

2'. In a radio system, an antenna array comprising a plurality ofantenna units, a translation device located at a point intermediate theends, of the array, separate lines each including an intermediatefrequency portion and a high frequency portion connecting saidtranslation device to each antenna suit, the intermediate frequencyportions of certain of said lines having lengths such that thephase-frequency characteristics of the paths traversed by the Wavecomponents intercepting said units and extending from the received wavefront to the translation device are substantially the same.

3. In a radio system, an antenna array comprising a plurality of antennaunits positioned to receive a desired Wave end on, a modulator and aphase changer for each unit at a terminal station located intermediatethe ends of said array, a translation device at said station, atransmission line for each unit consisting of a high frequency portionconnecting the unit to the corresponding modulator and an intermediatefrequency portion connecting the modulator to the corresponding hasechanger, and a common intermediate frequency line extending to saidtranslation device, said phase changers being connected to saidintermediate frequency line at points such that the paths traversed bythe wave components intercepting said units and extending from the wavefront to the translation device are substantially equal in electricallength.

4. In a radio system, an antenna array comprising a plurality of antennaunits, a modulator connected to each unit, a beat frequency oscillatorconnected to said modulators, the transmission lines extending from eachmodulator to the associated antenna unit and from each modulator to thebeat oscillator being substantially equal in length, a separate phasechanger connected to the output terminals of each modulator, and atranslation device connected to said phase changers.

5. In a radio system, an antenna array comprising a plurality of antennaunits, a translation device at a terminal station located intermediatethe ends of said array, a plurality of modulators at said terminalstation one for each of said units, a beat frequency oscillator at saidstation connected with each of said modulators, the transmission linesextending from each modulator to the corresponding antenna unit and fromeach modulator to the beat frequency oscillator being substantiallyequal in length, and a separate phase changer connected between eachmodulator output and said translation device.

6. In a radio system, an antenna array comprising a plurality of antennaunits, a terminal station located at a point intermediate the ends ofthe array, a plurality of modulators at said terminal station one foreach of said units, a line connecting each unit with its modulator, atranslation device at said station, a beat frequency oscillatorconnected to said modulators, each modulator being connected to saidoscillator through a length of transmission line such that thedifference between the lengths of the lines connecting successive pairsof units with their modulators taken pair by pair in one direction alongthe array plus the difference between the lengths of transmission linesconnecting the oscillator to the modulators of successive correspondingpairs of units taken in the other direc tion along the array shall equala constant having the same value for all the successive pairs of unitsalong the array, a connection between each modulator output and saidtranslation device, and a separate phase changer included in each ofsaid connections.

7. In a radio system, an antenna array com prising a pluralityof antennaunits positioned to receive a desired wave end on, a translation deviceat a terminal station located intermediate the ends of said array, amodulator at said station for each unit and having connection with suchunit, the paths traversed by the wave components intercepting said unitsand extending from the received wave front to the translation device byway of said modulators being substantially equal in length, a beatfrequency oscillator connected to said modulators, the transmissionlines extending from each modulator to the associated antenna unit andfrom each modulator to the beat oscillator being substantially equal inlength, and a separate phase changer connected between each modulatoroutput and said translation device.

8. The method of steering compensation for deviations from uniformity ofspacing with respect to the terminal station of the antenna units of. amultiple unit array, which consists in conducting to the terminalstation the signal frequencies received at the various units, modulatingeach signal frequency with a beating oscillator frequency conveyed overa transmission path equal in length in each case to the length oftransmission path from the corresponding unit to produce intermediatefrequencies of uniformly related phase differences, and controlling thephases of the intermediate frequencies for combination iii-phase at areceiver.

9. In a radio system, an array comprising at least two antenna unitsconnected to a translation device by separate lines of difierentphysical length, the wave velocity on said lines being different fromthe wave velocity in space, said physical length difference beingrelated to the angle between the array axis and the desired wavedirection and to the difference in said velocities, whereby the pathsextending from the desired wave front to said device and each in cludingan antenna unit and associated line have equal electrical lengths andequal phase-frequency or delay characteristics.

. 2,225,928 V 7-1 10,. In a radio system, a linear arraycomprisa givendirection, utilizing separate vlines'for connectingsaid'units to saidreceiver, which com- ,prises ascertaining the difierences in line lengthrequired to render"; equal inphysical length the ing a plurality ofantenna units connected by separate lines to a translation device, theanglebetween the array axis and the desired direction of radiation orreception being acute, the line and space velocities being different,the lines connected to adjacent units being adjusted.- to differ inactual length an amount dependent upon said angle and the differencebetween said velocities.

' phase currents at each frequencyin a; large band I 11. A method ofobtaining at a receiver inof frequencies from a signal wave interceptingthe antenna units of a lineararrayxand having paths traversed by thewave componentsandex' tending to the receiver from the wave front at theunit first intercepted, ascertaining the length correction necessary tocompensate for the difference in line and space velocities and connect iing lines having the ascertained lengths between 10 said units andreceiver.

DOUGLAS H. RING; v

